System and method for improved fluid delivery in multi-fluid injector systems

ABSTRACT

A method of maintaining an overall flow rate during a sequential delivery of at least two fluids to a patient&#39;s blood vessel includes delivering at least a first fluid into the patient&#39;s blood vessel at a first flow rate, delivering at least a second fluid into the patient&#39;s blood vessel at a second flow rate, and adjusting at least one of a first flow profile of the first flow rate and a second flow profile of the second flow rate to dampen a transient increase in the overall flow rate during a transition between delivering one of the first fluid and the second fluid to delivering the other of the first fluid and the second fluid.

CROSS REFERENCE TO RELATED APPLICATION

This application is a 371 national phase application of PCTInternational Application No. PCT/US2017/020637, filed Mar. 3, 2017, andclaims the benefit of U.S. Provisional Patent Application No.62/303,050, filed Mar. 3, 2016, the disclosure of which is herebyincorporated in its entirety by reference.

BACKGROUND Field of the Technology

The present disclosure is directed to a system and method for reducingthe occurrence of spikes in flow rates for a fluid delivery systemhaving a fluid pumping device for delivery of two or more medical fluidsin applications in medical diagnostic and therapeutic procedures.

Description of Related Art

In many medical diagnostic and therapeutic procedures, a physician ortrained clinician injects fluid into a patient. For example, a physicianmay inject saline and/or an imaging contrast medium into a patient tohelp improve the visibility of internal body structures during one ormore X-ray/CT imaging, MRI imaging, or other imaging procedure. Toinject the saline and/or contrast medium, the clinician may use a manualinjection syringe or may, alternatively, use a powered fluid injectionsystem. A catheter is coupled to the manual injection syringe orinjection device and is used to inject the saline and/or contrast mediuminto the patient (such as into a vessel in the patient's hand or arm).The contrast medium and saline are provided from separate sources, suchas bags, bottles, or syringes, and, in certain cases, may be mixedtogether before injection into the patient. However, several problemsmay develop during use of certain capacitive pressure injection systemsand syringes, including spikes in fluid flow rates, extravasation and/orinfiltration, saline or contrast medium contamination during injectiondue to backflow of the fluids, real-time injection ratio inaccuracies,or kick-back in catheter tubes that are inserted into patients.

A. Extravasation and Infiltration

Extravasation and infiltration are often characterized as an accidentalinfusion of an injection fluid, such as a contrast medium(extravasation) or saline (infiltration), into tissue surrounding ablood vessel rather than into the blood vessel itself. Extravasation andinfiltration can be caused, for example, by a fragile vascular system,valve disease, inaccurate needle placement, sudden changes in fluidflow, or patient movement resulting in the injected needle being pulledfrom the intended vessel or pushed through the wall of the vessel.

Additional extravasation and/or infiltration issues may occur when usingboth a contrast medium and saline for a procedure. As shown in FIG. 1,initially, no pressure is applied to the contrast medium 10 or saline12, resulting in no flow through the fluid injector system. As shown inFIG. 2, pressure is then applied to the contrast medium 10 resulting ina pressure build up and initial backflow of contrast medium 10 into thesaline 12 at point A. As a result, the flow rate of the contrast medium10 may be reduced due to the effect of backflow and expansion in thecontrast medium 10 bag or syringe and saline 12 bag or syringe due tothe injection fluid pressure. Further, the saline 12 bag or syringe mayexpand depending on the particular capacitance of the saline 12 bag orsyringe. As shown in FIG. 3, the flow rate and pressure of the contrastmedium 10 may continue to increase, thereby stabilizing the pressure inthe injector system. As shown in FIG. 4, due to the higher viscosity ofthe contrast medium 10, the pressure applied to the saline 12 must beincreased further until resistance to the flow of the saline 12 dropsand the saline 12 is directed into the contrast medium 10 flow at pointB. Until the saline 12 reaches a pressure that is substantially similarto the contrast medium 10, the saline 12 stores pressure energy duringthe contrast medium 10 injection. When the saline 12 piston beginsimmediately after the contrast medium 10 injection stops, however, theflow rate of the saline 12 increases rapidly (higher than the flow rateprogrammed for the saline 12) due to the stored pressure energy(capacitance), sending an increased amount of saline 12 to mix with thecontrast medium 10. This increased flow rate or flow spike can cause arapid fluid acceleration in the catheter. The syringes or bags of theinjector system will begin to deflate as the pressure within thesyringes or bags decreases due to the uniform flow of contrast medium 10and/or saline 12. The rapid increase in flow rate for the saline 12creates a transition to turbulence that causes the resistance toslightly rise again, causing oscillations in the flow. Eventually, astable flow rate is reached at a lower equilibrium pressure. However,due to the initial backflow and increased pressure in the fluid injectorsystem, an increased injection pressure and/or flow rate of contrastmedium 10 or saline 12 may be experienced.

B. Inaccurate Fluid Mixing Ratios

With further reference made to FIG. 1 and the injection processdescribed above, also due to the initial backflow and increased pressurein the fluid injector system, accurate flow rates of contrast medium 10and saline 12 are not always provided to the patient. Accurate flowrates of the contrast medium 10 and saline 12 may be achieved inaverage. However, for short periods of time until the system achievessteady state, the flow rates may be ramping, slowing down, peaking, andmay not be particularly precise. In one scenario, the contrast medium 10injection may be followed by the saline 12 injection, which causes asaline 12 overrate to the patient. In another scenario, a dual flowsimultaneous injection of the contrast medium 10 and the saline 12 maycause inaccurate ratios of the contrast medium 10 and saline 12 untilthe system stabilizes.

An additional factor that may contribute to the problem of inaccuratefluid mixing ratios is the backflow of fluid that occurs in injectionswhere the viscous contrast medium 10 is injected at a higher ratio thanthe less viscous saline 12. In such a scenario, before a uniform fluidflow is established, the fluid pressure of the more viscous contrastmedium 10 that is injected at a higher ratio may act against the fluidpressure of the less viscous saline 12 that is injected at a lower ratioto force the contrast medium 10 to reverse the desired direction offlow. After injection, pressures equalize and the fluid injection systemachieves a steady state operation where the contrast medium 10 andsaline 12 are injected at a desired ratio. However, in small volumeinjections, steady state operation may not be achieved prior to thecompletion of the injection process and the fluid mixing ratio ofcontrast medium 10 and saline 12 being delivered to the patient may notbe accurately achieved. Thus, even though a desired ratio of contrastmedium 10 and saline 12 may be 80% contrast medium 10 to 20% saline 12,the actual ratio due to backflow of contrast medium 10 into the saline12 may be higher. This problem is further compounded with an increase ininjection pressure. In one particular example of a fluid injectorsystem, the syringes are typically always pointing upwards and are usedfor multiple patients throughout an entire day. Therefore, contrastmedium 10 may backflow into the saline syringe and sink to the bottom ofthe saline syringe. By the time multiple patients have been treated andmultiple injections have been performed, the saline syringe may besubstantially filled with contrast medium thereby contaminating andreducing the amount of the saline fluid 12.

C. Catheter Kickback and Rapid Movement

An additional complication with known multi-fluid injector systems is akickback or rapid movement of the catheter in the patient's body as aresult of the erratic flow of the contrast medium or saline. In manyknown multi-fluid injector systems, the saline and contrast mediumtubing is connected to a catheter that is used for injecting the fluidsinto the patient. However, due to the backflow of the saline and/orcontrast medium and the rapid acceleration of contrast medium or salineinto the fluid line of the multi-fluid injector system during fluidtransitions, the catheter may at least partially kick-back or otherwisechange position within the patient vasculature. Fluid accelerations maybe caused by nozzle effects in the catheter and rapid increases in flowrate during contrast medium-to-saline transitions. The nozzle on thecatheter may accelerate the fluid from a lower flow rate in the tubingof the catheter to an increased flow rate exiting the catheter. Thetransition from a contrast medium injection to a saline injection causesa rapid flow rate increase. The force imparted to the catheter may causeundesired movement of the catheter. Complications related toextravasation and infiltration, inaccurate fluid mixing ratios, andcatheter kickback and rapid movement may include unnecessary pain anddiscomfort to the patient. There is a current need for a system thatprovides accurate flow rates of saline and/or contrast medium to apatient, thereby reducing the risk of extravasation and/or infiltration.There is also a current need for a catheter design that reduces kickbackand rapid movement of the catheter during injection of a fluid into apatient's blood vessel.

BRIEF SUMMARY

In view of the foregoing, a need exists for an improved fluid deliverysystem for fluid delivery applications in medical diagnostic andtherapeutic procedures. There is an additional need in the medical fieldfor a fluid delivery system that provides a more precise and efficientflow rate or ratio of fluids during initial injection procedurescompared to existing fluid delivery systems. Existing fluid deliverysystems do not always provide accurate flow rates or mixing ratios ofthe desired fluids resulting in the risk of extravasation and/orinfiltration. There is a current need for a fluid delivery system thatallows an individual to quickly and accurately provide the necessaryflow rate or ratio of fluids to a patient.

In one example, a method of maintaining a substantially uniform overallflow rate during a sequential delivery of at least two fluids to apatient's blood vessel includes delivering at least a first fluid intothe patient's blood vessel at a first flow rate, delivering at least asecond fluid into the patient's blood vessel at a second flow rate, andadjusting at least one of a first flow profile of the first flow rateand a second flow profile of the second flow rate to dampen a transientincrease in the overall flow rate during a transition between deliveringone of the first fluid and the second fluid to delivering the other ofthe first fluid and the second fluid.

In another example, the method further includes delaying the delivery ofone of the first fluid and the second fluid until the other of the firstfluid and the second fluid reaches a predetermined flow rate. The methodmay include adjusting one of the first flow rate and the second flowrate using a controller based on the other of the first flow rate andthe second flow rate. The method may include pressurizing the firstfluid using a check valve to a predetermined pressure before deliveringthe first fluid. The method may include pressurizing the second fluidusing a check valve to a predetermined pressure before delivering thesecond fluid. The method may include pressurizing the first fluid andthe second fluid using separate check valves to a first predeterminedpressure and a second predetermined pressure, respectively, beforedelivering the first fluid and the second fluid.

The method may include over-delivering a predetermined volume of atleast one of the first fluid and the second fluid during the delivery ofat least one of the first fluid and the second fluid. The method mayinclude diluting one of the first fluid and the second fluid with apredetermined volume of the other of the first fluid and the secondfluid.

The method may include providing a multi-fluid injection systemincluding a first syringe for receiving the first fluid and a firstplunger movable within a barrel of the first syringe to pressurize thefirst fluid for delivery to the patient's blood vessel, and a secondsyringe for receiving the second fluid and a second plunger movablewithin a barrel of the second syringe to pressurize the second fluid fordelivery to the patient's blood vessel, and reducing a capacitance of atleast one of the first syringe and the second syringe to preventbackflow of at least one of the second fluid into the first syringe andthe first fluid into the second syringe. The method may includeproviding a pressure jacket around an outer circumference of at leastone of the first syringe and the second syringe to reduce swelling of atleast one of the first syringe and the second syringe under pressure.

The method may include providing a multi-fluid injection systemincluding a first syringe for receiving the first fluid and a firstplunger movable within a barrel of the first syringe to pressurize thefirst fluid for delivery to the patient's blood vessel, and a secondsyringe for receiving the second fluid and a second plunger movablewithin a barrel of the second syringe to pressurize the second fluid fordelivery to the patient's blood vessel, and wherein at least one of thefirst syringe and the second syringe includes a reduced inside diameterto correspond to a desired flow rate. The method may include providingan obstruction member within at least one of the first syringe and thesecond syringe to reduce the inner diameter of at least one of the firstsyringe and the second syringe.

The method may include providing a multi-fluid injection systemincluding a first syringe for receiving the first fluid and a firstplunger movable within a barrel of the first syringe to pressurize thefirst fluid for delivery to the patient's blood vessel, and a secondsyringe for receiving the second fluid and a second plunger movablewithin a barrel of the second syringe to pressurize the second fluid fordelivery to the patient's blood vessel, and providing an externalrestriction member on an outer circumference of at least one of thefirst syringe and the second syringe; and adjusting an inner diameter ofthe external restriction member to adjust a permitted swelling of atleast one of the first syringe and the second syringe.

The method may include controlling one of the first flow rate and thesecond flow rate using an equalizing flow valve based on the other ofthe first flow rate and the second flow rate. The method may includeadjusting at least one of the first flow rate and the second flow ratebefore delivery of at least one of the first fluid and the second fluidbased on at least one of known operating fluid pressure and capacitanceof a multi-fluid injection system used to deliver the first fluid andthe second fluid. The method may include increasing a transition timebetween delivering one of the first fluid and the second fluid anddelivering the other of first fluid and the second fluid.

In another example, a controller for a multi-fluid injection systemconfigured to maintain an overall flow rate during a sequential deliveryof at least two fluids to a patient's blood vessel, the system includesa processor configured to control the multi-fluid injection system to:deliver at least a first fluid into the patient's blood vessel at afirst flow rate, deliver at least a second fluid into the patient'sblood vessel at a second flow rate, and adjust at least one of a firstflow profile of the first flow rate and a second flow profile of thesecond flow rate to dampen a transient increase in the overall flow rateduring a transition between delivering one of the first fluid and thesecond fluid to delivering the other of the first fluid and the secondfluid.

In another example, the processor is further configured to control themulti-fluid injection system to increase a transition time betweendelivering one of the first fluid and the second fluid and deliveringthe other of the first fluid and the second fluid. The processor mayalso be further configured to control the multi-fluid injection systemto delay the delivery of one of the first fluid and the second fluiduntil the other of the first fluid and the second fluid reaches apredetermined flow rate. The processor may also be further configured tocontrol the multi-fluid injection system to over-deliver a predeterminedvolume of at least one of the first fluid and the second fluid duringdelivery of at least one of the first fluid and the second fluid.

Further examples will now be described in the following numberedclauses.

Clause 1: A method of maintaining an overall flow rate during asequential delivery of at least two fluids to a patient's blood vessel,the method comprising: delivering at least a first fluid into thepatient's blood vessel at a first flow rate; delivering at least asecond fluid into the patient's blood vessel at a second flow rate; andadjusting at least one of a first flow profile of the first flow rateand a second flow profile of the second flow rate to dampen a transientincrease in the overall flow rate during a transition between deliveringone of the first fluid and the second fluid to delivering the other ofthe first fluid and the second fluid.

Clause 2: The method of Clause 1, wherein adjusting at least one of thefirst flow profile of the first flow rate and a second flow profile ofthe second flow rate comprises delaying the delivery of one of the firstfluid and the second fluid until the other of the first fluid and thesecond fluid reaches a predetermined flow rate.

Clause 3: The method of Clause 1 or Clause 2, wherein adjusting at leastone of the first flow profile of the first flow rate and a second flowprofile of the second flow rate comprises adjusting one of the firstflow rate and the second flow rate using a controller based on the otherof the first flow rate and the second flow rate.

Clause 4: The method of any of Clauses 1-3, further comprisingpressurizing the first fluid using a check valve to a predeterminedpressure before delivering the first fluid.

Clause 5: The method of any of Clauses 1-4, further comprisingpressurizing the second fluid using a check valve to a predeterminedpressure before delivering the second fluid.

Clause 6: The method of any of Clauses 1-5, further comprisingpressurizing the first fluid and the second fluid using separate checkvalves to a first predetermined pressure and a second predeterminedpressure, respectively, before delivering the first fluid and the secondfluid.

Clause 7: The method of any of Clauses 1-6, wherein adjusting at leastone of the first flow profile of the first flow rate and a second flowprofile of the second flow rate comprises over-delivering apredetermined volume of at least one of the first fluid and the secondfluid during the delivery of at least one of the first fluid and thesecond fluid.

Clause 8: The method of any of Clauses 1-7, further comprising dilutingone of the first fluid and the second fluid with a predetermined volumeof the other of the first fluid and the second fluid.

Clause 9: The method of any of Clauses 1-8, further comprising:providing a multi-fluid injection system comprising: a first syringe forreceiving the first fluid and a first plunger movable within a barrel ofthe first syringe to pressurize the first fluid for delivery to thepatient's blood vessel; and a second syringe for receiving the secondfluid and a second plunger movable within a barrel of the second syringeto pressurize the second fluid for delivery to the patient's bloodvessel; and reducing a capacitance of at least one of the first syringeand the second syringe to prevent backflow of at least one of the secondfluid into the first syringe and the first fluid into the secondsyringe.

Clause 10: The method of Clause 9, further comprising providing apressure jacket around an outer circumference of at least one of thefirst syringe and the second syringe to reduce swelling of at least oneof the first syringe and the second syringe under pressure.

Clause 11: The method of any of Clauses 1-10, further comprising:providing a multi-fluid injection system comprising: a first syringe forreceiving the first fluid and a first plunger movable within a barrel ofthe first syringe to pressurize the first fluid for delivery to thepatient's blood vessel; and a second syringe for receiving the secondfluid and a second plunger movable within a barrel of the second syringeto pressurize the second fluid for delivery to the patient's bloodvessel; and wherein at least one of the first syringe and the secondsyringe includes a reduced inside diameter to correspond to a desiredflow rate.

Clause 12: The method of Clause 11, further comprising providing anobstruction member within at least one of the first syringe and thesecond syringe to reduce the inner diameter of at least one of the firstsyringe and the second syringe.

Clause 13: The method of any of Clauses 1-12, further comprising:providing a multi-fluid injection system comprising: a first syringe forreceiving the first fluid and a first plunger movable within a barrel ofthe first syringe to pressurize the first fluid for delivery to thepatient's blood vessel; and a second syringe for receiving the secondfluid and a second plunger movable within a barrel of the second syringeto pressurize the second fluid for delivery to the patient's bloodvessel; providing an external restriction member on an outercircumference of at least one of the first syringe and the secondsyringe; and adjusting an inner diameter of the external restrictionmember to adjust a permitted swelling of at least one of the firstsyringe and the second syringe.

Clause 14: The method of any of Clauses 1-13, wherein adjusting at leastone of the first flow profile of the first flow rate and a second flowprofile of the second flow rate comprises controlling one of the firstflow rate and the second flow rate using an equalizing flow valve basedon the other of the first flow rate and the second flow rate.

Clause 15: The method of any of Clauses 1-14, wherein adjusting at leastone of the first flow profile of the first flow rate and a second flowprofile of the second flow rate comprises adjusting at least one of thefirst flow rate and the second flow rate before delivery of at least oneof the first fluid and the second fluid based on at least one of knownoperating fluid pressure and capacitance of a multi-fluid injectionsystem used to deliver the first fluid and the second fluid.

Clause 16: The method of any of Clauses 1-15, wherein adjusting at leastone of the first flow profile of the first flow rate and a second flowprofile of the second flow rate comprises increasing a transition timebetween delivering one of the first fluid and the second fluid anddelivering the other of first fluid and the second fluid.

Clause 17: A multi-fluid injection system configured to maintain anoverall flow rate during a sequential delivery of at least two fluids toa patient's blood vessel, the system comprising: a processor configuredto control the multi-fluid injection system to: deliver at least a firstfluid into the patient's blood vessel at a first flow rate; deliver atleast a second fluid into the patient's blood vessel at a second flowrate; and adjust at least one of a first flow profile of the first flowrate and a second flow profile of the second flow rate to dampen atransient increase in the overall flow rate during a transition betweendelivering one of the first fluid and the second fluid to delivering theother of the first fluid and the second fluid.

Clause 18: The controller of Clause 17, wherein the processor is furtherconfigured to control the multi-fluid injection system to increase atransition time between delivering one of the first fluid and the secondfluid and delivering the other of the first fluid and the second fluid.

Clause 19: The controller as claimed in Clause 17 or Clause 18, whereinthe processor is further configured to control the multi-fluid injectionsystem to delay the delivery of one of the first fluid and the secondfluid until the other of the first fluid and the second fluid reaches apredetermined flow rate.

Clause 20: The controller as claimed in any of Clauses 17-19, whereinthe processor is further configured to control the multi-fluid injectionsystem to over-deliver a predetermined volume of at least one of thefirst fluid and the second fluid during delivery of at least one of thefirst fluid and the second fluid.

These and other features and characteristics of the fluid injectionsystem, as well as the methods of operation and functions of the relatedelements of structures and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claim with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only, andare not intended as a definition of the limits of the disclosure. Asused in the specification and the claim, the singular form of “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are schematic views depicting known methods of injecting afirst fluid and a second fluid to a patient using a fluid injectionsystem;

FIGS. 5 and 6 are schematic views depicting a fluid injection systemaccording to one example of the present disclosure;

FIG. 7 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 8 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 9 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 10 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure showing a plunger in anextended position;

FIG. 11 is a schematic view depicting the fluid injection system of FIG.10 with the plunger in an over-travel position;

FIG. 12 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 13 is a front view of a syringe according to an example of thepresent disclosure;

FIG. 14 is a cross-sectional view depicting a syringe of a fluidinjection system according to another example of the present disclosurealong line A-A in FIG. 13;

FIG. 15 is a cross-sectional view depicting a syringe of a fluidinjection system according to another example of the present disclosure;

FIG. 16 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 17 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 18 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure;

FIG. 19 is a front view of a catheter including a rigid member accordingto another example of the present disclosure;

FIG. 20A is a front view of a catheter including a sheath provided on anouter circumferential surface thereof in a deflated position;

FIG. 20B is a front view of the catheter and sheath of FIG. 20A in aninflated position;

FIGS. 21 and 22 are front views of a catheter according to anotherexample of the present disclosure;

FIGS. 23 and 24 are front views of a catheter according to anotherexample of the present disclosure;

FIG. 25 is a cross-sectional view of a catheter according to anotherexample of the present disclosure;

FIGS. 26 and 27 are cross-sectional views of a catheter inserted into apatient's blood vessel according to another example of the presentdisclosure;

FIG. 28 is a graphical illustration of a transition period betweeninjecting contrast medium and injecting saline during currentmulti-fluid injection procedures;

FIG. 29 is a graphical illustration of an extended transition periodbetween injecting contrast medium and injecting saline according to thepresent disclosure;

FIG. 30 is a perspective view of a multi-fluid injection systemaccording to an example of the present disclosure;

FIG. 31 is a graph depicting an overall flow rate of fluid exiting acatheter with a contrast medium to saline transition;

FIG. 32 is a graph depicting an overall flow rate of fluid exiting acatheter with a saline to saline transition;

FIG. 33 is an annotated graph depicting an overall flow rate of fluidexiting a catheter with a contrast medium to saline transition;

FIG. 34 is a graph depicting several different overall catheterflowrates of varying contrast medium viscosity;

FIG. 35 is a graph depicting several different overall catheterflowrates;

FIG. 36A is a schematic of a multi-fluid injection system according toan example of the present disclosure;

FIG. 36B is a cross-sectional view of the multi-fluid injection systemof FIG. 30; and

FIG. 37 is a schematic view depicting a fluid injection system accordingto another example of the present disclosure.

DESCRIPTION OF THE DISCLOSURE

For the purposes of the description hereinafter, spatial orientationterms, if used, shall relate to the referenced example as it is orientedin the accompanying drawings, figures, or otherwise described in thefollowing detailed description. However, it is to be understood that theexamples described hereinafter may assume many alternative variationsand examples. It is also to be understood that the specific systemsillustrated in the accompanying drawings, figures, and described hereinare simply exemplary and should not be considered as limiting.

Referring to the drawings in which like reference characters refer tolike parts throughout the several views thereof, several systems andmethods are provided for reducing incidences of infiltration and/orextravasation, reducing the occurrence of spikes or sudden changes influid flow rates during an injection procedure, ensuring accurate flowrates and mixing ratios of fluids are delivered to the patient, andreducing kickback and rapid movement of a catheter during a transitionfrom one injected fluid to another fluid. In a typical multi-fluidinjection procedure, an injection fluid, such as a contrast medium, isdelivered from a contrast medium source to the patient using a poweredor manual injector. The injected contrast medium is delivered to adesired site in a patient's body through a catheter inserted into thepatient's body, such as the arm. Once the contrast medium is deliveredto the desired site, the area is imaged using a conventional imagingtechnique, such as computed tomography (CT), angiography imagining,magnetic resonance imaging (MRI), or other imaging or scanningtechnique. The contrast medium becomes clearly visible against thebackground of the surrounding tissue. However because the contrastmedium may comprise toxic substances, it is desirable to reduce contrastdosing to the patient, while maintaining an effective contrast amountnecessary for accurate imaging. By supplementing an overall contrastmedium delivery procedure with saline, the saline flushes the contrastmedium to the area of interest and additional hydration of the patientoccurs automatically and aids the body in removing the contrast medium.In addition to improved patient comfort level and less toxicity,introduction of saline at clinically significant pressures and flowrates also allows higher flow rates to be achieved at lower pressuresettings on the injector.

In one example, as shown in FIG. 30, a fluid injector 100 (hereinafterreferred to as “injector 100”), such as an automated or powered fluidinjector, is adapted to interface with and actuate at least one syringe102, each of which may be independently filled with a medical fluid,such as contrast medium, saline solution, or any desired medical fluid.The injector 100 may be used during a medical procedure as describedherein to inject the medical fluid into the body of a patient by drivinga plunger 104 of the at least one syringe 102 with at least one piston(not shown). The injector 100 may be a multi-syringe injector, whereinseveral syringes 102 may be oriented in a side-by-side or otherarrangement and include plungers 104 separately actuated by respectivepistons associated with the injector 100. In examples with two syringesarranged in a side-by-side relationship and filled with two differentmedical fluids, the injector 100 may deliver fluid from one or both ofthe syringes 102. The injector 100 has a control mechanism 106 forcontrolling operation of at least one operating parameter of injector100, such as the injection pressure, volume, and/or flow rate of fluiddelivered from at least one of the syringes 102.

The injector 100 has a housing 108 formed from a suitable structuralmaterial, such as plastic or metal, that encloses various components fordelivering fluid from the syringes 102. The housing 108 may have variousshapes and sizes depending on a desired application. The injector 100includes at least one syringe port 110 for connecting the at least onesyringe 102 to respective piston elements. In some examples, the atleast one syringe 102 includes at least one syringe retaining member forretaining the syringe 102 within a syringe port 110 of the injector 100.The at least one syringe retaining member operatively engages a lockingmechanism provided on or in the syringe port 110 of the injector 100 tofacilitate loading and/or removal of the syringe 102 to and from theinjector 100.

At least one fluid path set 112 may be fluidly connected with the atleast one syringe 102 for delivering medical fluid from the at least onesyringe 102 to a catheter, needle, or other fluid delivery device (notshown) inserted into a patient at a vascular access site. Fluid flowfrom the at least one syringe 102 may be regulated by a fluid controlmodule. The fluid control module may operate various pistons, valves,and/or flow regulating structures to regulate the delivery of themedical fluid, such as saline solution and contrast medium, to thepatient based on user selected injection parameters, such as injectionflow rate, duration, total injection volume, and/or ratio of contrastmedium and saline. An example of a suitable front-loading fluid injector100 that may be modified for use with the above-described systemincluding at least one syringe 102 and at least one syringe interfaceloading and releasable retaining of the at least one syringe 102 withthe fluid injector 100 described herein with reference to FIG. 33 isdisclosed in U.S. Pat. No. 5,383,858 to Reilly et al.; U.S. Pat. No.9,173,995 to Tucker et al.; and U.S. Pat. No. 9,199,033 to Cowen et al.,each of which are incorporated herein by reference in their entirety.Another example of a multi-fluid delivery systems that may be modifiedfor use with the present system is found in U.S. Pat. No. 7,553,294 toLazzaro et al.; U.S. Pat. No. 7,666,169 to Cowan et al.; InternationalPatent Publication No. WO 2012/155035; and United States PatentApplication Publication No. 2014/0027009 to Riley et al.; thedisclosures of which are incorporated herein by reference.

To enable effective simultaneous flow delivery of first and secondinjection fluids, such as contrast and saline, substantially equalpressure must be present in each delivery line. In a powered injectionsystems described herein, in a dual flow mode it is desirable to actuatethe plunger elements substantially simultaneously in simultaneous flowdelivery applications to equalize the pressure in each line.Alternatively, in a single flow mode, one plunger element is actuated todeliver the desired fluid while the other plunger element is held inplace. If the injector is operated with differential pressure in eachdelivery line of the fluid path set, fluid in the lower pressure linemay be stopped or reversed until sufficient pressure is achieved in thelower pressure line to enable flow in a desired direction. This timedelay could reduce the image quality. The fluid in the lower pressureside may also begin to store fluid pressure energy against the fluid inthe higher pressure line. As the stored fluid pressure energy in thelower pressure side continues to build, the lower pressure willeventually achieve the same pressure as the higher pressure fluid as itexits into the catheter tubing. Due to the stored fluid pressure energyin the lower pressure side, the flow rate of the lower pressure fluidcan rapidly accelerate into the catheter tubing, particularly when thepressure in the high pressure fluid is reduced.

As shown in FIGS. 31 and 33, when delivering contrast medium and,subsequently, saline solution to a patient's blood vessel, a spike orsudden increase in an overall flow rate of fluid exiting the cathetermay be experienced during a flow transition between the contrast mediumand the saline. In one example, an overall flow rate through thecatheter is understood to be the combined flow rate of the first fluid(in one example, saline solution) and the second fluid (in one example,contrast medium) exiting from the catheter. In one example, in whichthere is no flow of contrast medium through the catheter, the overallflow rate is equal to the flow rate of the saline solution. In anotherexample, in which there is no flow of saline solution through thecatheter, the overall flow rate is equal to the flow rate of thecontrast medium. In another example, in which there is flow of salinesolution and contrast medium through the catheter, the overall flow rateis equal to the combined flow rates of the saline solution and thecontrast medium. Therefore, a fluid system may have a first flow ratecorresponding to the flow rate of the first fluid, a second flow ratecorresponding to the flow rate of the second fluid, and an overall flowrate corresponding to the combination of flow rates of the first andsecond fluids. As shown in FIGS. 31 and 33, as the contrast medium isinitially directed through the catheter, the overall flow rate of thesystem equals the flow rate of the contrast medium and graduallyincreases to a desired steady-state flow rate. In FIG. 33, in oneexample, the desired overall flow rate exiting the catheter is 3 mL/s.Once a sufficient volume of contrast medium has been directed throughthe catheter and into the patient's blood vessel, a volume of salinesolution is subsequently directed through the catheter to flush thecontrast into the patient. As the delivery of the more viscous contrastmedium transitions to the delivery of less viscous saline solution fromthe catheter, a sudden spike or increase in the overall flow rate isexperienced in the system. As shown in FIG. 33, this spike or increasein the overall flow rate lasts for a specified duration and increasesthe overall flow rate of the system to a flow rate greater than thedesired overall flow rate. As shown, the overall flow rate may increaseto 5.5 mL/s, which is 2.5 mL/s higher than desired for the injectionprotocol. Therefore, it is an object of the present disclosure to dampenthe sudden spike or increase in the overall flow rate exiting thecatheter, for example by reducing the height of the spike and/or theduration of the spike, by adjusting a flow profile of the salinesolution and/or the flow profile of the contrast medium during atransition between the delivery of the contrast medium to the deliveryof the saline solution. Several different methods and arrangements fordampening the increase in overall flow rate exiting the catheter andreducing the duration of the increased overall flow rate are describedbelow.

As shown in FIG. 32, in a system delivering only saline solution to apatient, there is no sudden spike or increase observed in the overallflow rate exiting the catheter when switching from one saline syringe toanother. In fact, the system may experience a slight temporary decreasein the overall flow rate exiting the catheter. As shown in FIG. 34, thedifference in viscosity of the contrast medium used in the systemcompared to that of the saline (Δ-Viscosity) may also affect theseverity of the sudden spike or increase in the overall flow rateexiting the catheter. For example, a contrast medium with a higherviscosity (e.g., 26 cP) may contribute to a larger spike or increase inthe overall flow rate exiting from the catheter than a contrast mediumwith a lower viscosity (e.g., 10 cP). As shown in FIG. 35, the desiredoverall flow rate of the fluid exiting from the catheter may also affectthe severity of the sudden spike or increase in the overall flow rateexiting the catheter. For example, a higher desired overall flow rate(e.g., 5 mL/s) may contribute to a larger spike or increase in theoverall flow rate exiting from the catheter than a lower desired overallflow rate (e.g., 2 mL/s).

Further, the fluid mixing ratio of contrast medium-to-saline may becomeinaccurate due to the stored fluid pressure energy in the lower pressuresaline syringe or line. The contrast medium may be injected at asignificantly higher ratio relative to saline, such as 80% contrastmedium to 20% saline injection protocol. The flow reversal may beexacerbated at high injection pressures. In small dosage injections at ahigh injection pressure, flow reversal may effectively stop the deliveryof saline such that up to 100% contrast medium is injected, rather thanthe desired 80% contrast medium to 20% saline ratio. Similarinaccuracies may occur at various other injection protocols, including,but not limited to 20% contrast medium to 80% saline ratio.

The above-described situation of flow reversal during powered injectionsat high contrast medium-to-saline ratio may occur at least in part dueto injection system capacitance. Total system capacitance (also referredto as compliance or the ability to store a fluid volume and/or hydraulicenergy) represents the amount of suppressed fluid (i.e., backflowvolume) that is captured in the swelling of the fluid injector systemcomponents or compression of fluid injector system components, such asthe fluid lines and/or syringe(s) due to pressure applied to a medicalfluid during an injection process. Total system capacitance is inherentto each fluid injection system and depends on a plurality of factors,including injector construction, mechanical properties of materials usedto construct the syringe, plunger, pressure jacket surrounding thesyringe, fluid lines delivering the contrast medium and saline to a flowmixing device, size or surface area of the syringe, plunger, pressurejacket, compression or deflection of syringe injector components, etc.The amount of back or reverse flow increases when the relative speeddifference between the two plungers is large, the simultaneous fluidflow is through a small restriction, the speed of the total fluidinjection is large, and/or the viscosity of the fluid is high. The backor reverse flow can prevent different ratios of simultaneously deliveredfluid from occurring in certain injections, which can be a detriment fortwo-syringe type fluid injector systems.

In general, capacitance is directly correlative to injection pressureand inversely correlative to volume of contrast medium and saline in thesyringes. For example, in one example, capacitance during an injectionat 1200 psi with 150 mL of contrast medium and saline remaining incertain medical injector syringes is around 10 mL. In another example,the capacitance volume can be from about 5 mL to about 9 mL. Capacitanceis also a function of the ratio at which the first and second injectionfluids, such as contrast and saline, are injected. At a 50%-50% ratio,where contrast and saline are injected in equal amounts, backflow volumeis minimized because the capacitance on the contrast medium side isequal to the capacitance on the saline side of the fluid injectionsystem such that substantially equal pressures are present in eachdelivery line. Backflow may occur in situations where first and secondinjection fluids are delivered through long fluid conduits. However, asthe injection ratio of contrast and saline changes, backflow volumeincreases corresponding to the increase in the ratio.

With reference to FIG. 36, capacitance in a particular injector systemcan occur in several different locations during an injection procedureof the system. In particular, in one example, the catheter tubing 200 ofthe system may experience swelling and/or compression during aninjection procedure, which can affect the flow rates of the fluidsthrough the tubing 200. In another example, the catheter 210 itself mayexperience swelling and/or compression during an injection procedure,which can affect the flow rate of the fluid exiting the catheter 210. Inanother example, the syringe 220 of the injector system may experienceswelling and/or compression during an injection procedure. The swellingof the syringe 220 may occur in the form of radial expansion and/oraxial expansion of the syringe 220. In another example, the syringeinterface 230 may experience swelling and/or compression during aninjection procedure. The syringe interface 230 is the connection betweenthe syringe 220 and the injector system. In one example, the syringeinterface 230 may include locking mechanisms, O-rings or other sealingmembers that can experience swelling and/or compression during theinjection procedure. In another example, locking features 235 on thesyringe, such as flanges or lugs may compress or bend under the appliedpressure. In another example, a piston head 240 in the injector systemmay experience swelling and/or compression during an injectionprocedure, for example if there is mechanical play between the pistonhead 240 and the corresponding syringe plunger. Due to the forcesexerted by and on the piston head 240, compression forces may createswelling in the piston head 240. In another example, the piston 250 mayexperience bending, torqueing, swelling and/or compression during aninjection procedure. Due to the forces exerted by and on the piston 250,compression forces may create swelling in the piston 250 andcorresponding reduction in piston length. In another example where apolymeric cover 260 is provided on piston head 240 or syringe plungerassembly, the polymeric cover 260 may experience swelling and/orcompression during an injection procedure. In another example, a straingauge cap 270 positioned in the injector system on an end of piston 250may experience swelling and/or compression during an injectionprocedure. Although the strain gauge cap 270 is configured to stretch tomeasure strain in piston 250, the injection procedure may createadditional swelling and/or compression in the strain gauge cap 270. Oneor more of these or other factors (such as compression of the medicalfluid or gas bubbles therein) may contribute to the overall capacitancevolume of an injector system. Depending on the type of injectionprocedure or system, all of these factors may contribute to overallcapacitance of the injector system or only a subset of these factors maycontribute to overall capacitance of the injector system. The value ofthe contribution of each factor may differ from other factors.

While several different factors that can affect the overall flow rate oran individual flow rate of one of the fluids in the injector system havebeen described, it is also contemplated that other factors may alsoaffect these flow rates. The state of the particular flow of fluidthrough the injector system and the particular flow transition physics(laminar versus turbulent flow) during fluid mixing, fluid flow pastfluid path components, and exiting from the catheter into the patient'sblood vessel, the temperature of the contrast medium may increase theviscosity of the contrast medium, and the higher flow rates for cardiacCT and other advanced imaging applications may also affect these flowrates.

A. Solutions for Reducing Spikes in Fluid Flow Rates and ProvidingAccurate Mixing Fluid Ratios

Solutions to the problem of reducing backflow to compensate for systemcapacitance, for example in a high contrast medium-to-saline ratio, andthereby reducing undesired spikes in fluid flow rates and providing moreaccurate mixing ratios of fluids to the patient are described herein. Inall of the examples described herein, a fluid flow profile of at leastone of a first fluid 30 and a second fluid 32 is adjusted based on afunction of the flow rate of one of the first fluid 30 and the secondfluid 32 to minimize or dampen the spike or increase in the overall flowrate of fluid exiting from the catheter during a transition betweendelivering one of the first fluid 30 and the second fluid 32 todelivering the other of the first fluid 30 and the second fluid 32.

In one embodiment, one solution for improving (i.e., reducing) theoverall capacitance of the injector system is to increase the stiffnessof one or more of the components of the injector system subject tocapacitance, to reduce swelling and/or compression in the one or morecomponents. In one example, the stiffness of one of the catheter tubing200, the catheter 210, the syringe 220, the syringe interface 230, thepiston head 240, the piston 250, the polymeric cover 260, and the straingauge cap 270 may be increased to reduce swelling and/or compression inthe components of the injector system. In another embodiment, a pressurejacket may be placed around an outer surface of syringe 220 to reduceradial swelling under injection pressure.

The various embodiments of the methods described herein may be appliedto injection procedures including simultaneous injection of fluid fromtwo or more syringes or, alternatively, to reduce pressure and fluidflow spikes associated with transition from one fluid to another fluidduring sequential injection of two or more fluids from two or moresyringes, for example when transitioning from a contrast injection to asaline injection, or vice versa.

As shown in FIGS. 5 and 6, due to the additional time that is needed forthe correct pressure to be achieved in the less viscous first fluid 20,various embodiments of the methods herein include delaying or rampingthe application of pressure to the second fluid 22 until the pressure ofthe first fluid 20 has reached a predetermined pressure. Thispredetermined pressure may be a low equilibrium pressure that provides asmooth flow rate of fluid through the fluid injection system. In oneexample, the second fluid 22 may be more viscous than the first fluid20. In one example, the second fluid 22 may be contrast medium and thefirst fluid 20 may be saline. As shown in FIG. 5, initially, pressuremay be applied to the first fluid 20 via a plunger 26 until the pressureof the first fluid 20 has reached the predetermined pressure. As shownin FIG. 6, after the first fluid 20 has reached the predeterminedpressure, the same predetermined pressure may be applied to the secondfluid 22 via a plunger 28, resulting in the first fluid 20 and thesecond fluid 22 having a substantially similar flow rate through thefluid injection system. This system and method reduces the rapidincreases in first fluid 20 pressure through the fluid injection system,which often causes erratic flow and inaccurate volumes of the firstfluid 20 and the second fluid 22 being injected in the patient. Byallowing the pressure of the first fluid 20 to reach a predeterminedpressure before the second fluid 22, the first fluid 20 and the secondfluid 22 can reach the same predetermined pressure at substantially thesame time. The predetermined pressure will be dependent upon severalfactors, including, among others, the diameter of the catheter that isused to inject the first fluid 20 and the second fluid 22 into thepatient, the viscosity of the first fluid 20 and the second fluid 22,the capacitance of the first fluid 20 and the second fluid 22 syringesand overall capacitance of the injector system, and/or the innerdiameter of the tubing used to deliver the first fluid 20 and the secondfluid 22 to the catheter. It is also contemplated that this fluidinjection system may be automated with the use of a controller 24 thatcontrols the actuation of each of a pair of motors 25, 27 that areconfigured to move the pair of plungers 26, 28 that are used to applypressure to the first fluid 20 and the second fluid 22. In this example,the controller 24 may be programmed to delay applying or ramping theapplication of pressure to the second fluid 22 until the first fluid 20has reached the predetermined pressure. The controller 24 may be aprocessor configured to store several different protocols for injectionprocedures based upon one or more of predetermined pressures for thefluid injection system, syringe volumes, catheter, the first fluid 20type and/or volume to be delivered, the second fluid 22 type and/orvolume to be delivered, flow rates of the first fluid 20 and/or thesecond fluid 22, system capacitance, fluid temperature, tubing typeand/or diameter, and/or patient depending on the procedure. In oneexample, a user of the fluid injection system may input this identifyinginformation into the controller 24, which will calculate the properpredetermined pressure to apply to the first fluid 20 and the secondfluid 22 during the injection procedure to minimize pressure and flowspikes at fluid transitions. In an alternative example, the first fluid20 may be more viscous than the second fluid 22. In this example, theprocess described above in reference to FIGS. 5 and 6, would be switchedto apply an initial pressure to the second fluid 22 before applyingpressure to the first fluid 20. It is also contemplated that the firstfluid 20 and the second fluid 22 may have substantially equalviscosities. In this example, equal pressures may be applied to thefirst fluid 20 and the second fluid 22 at the outset of the process.

With reference to FIG. 7, another method for reducing undesired spikesin fluid flow rates and providing more accurate fluid mixing ratios withthe fluid injection system is described. A first fluid 30 and a secondfluid 32 may be provided in a fluid injection system in which plungers34, 36 driven by motors 35, 37 apply pressure to the first fluid 30 andthe second fluid 32, respectively. In one example, the second fluid 32may be more viscous than the first fluid 30. The second fluid 32 may becontrast medium and the first fluid 30 may be saline. A controller 38may be operatively connected to the motors 35, 37 to control the rate ofpressure applied to the first fluid 30 and the second fluid 32 by theplungers 34, 36. The controller 38 may be programmed to apply pressureto the first fluid 30 based on the pressure that is being applied to thesecond fluid 32. As the second fluid 32 is pushed through the fluidinjection system, the controller 38 may correspondingly change thepressure applied to the first fluid 30 by the plunger 34. For example,if a certain pressure is being applied to the second fluid 32 by theplunger 36, the controller 38 may instruct the plunger 34 to apply aproportionally larger pressure to the first fluid 30 to compensate forthe resistance of the more viscous second fluid 32. Using the controller38 in this manner, the first fluid 30 and the second fluid 32 may flowthrough the fluid injection system at substantially equal flow rates,thereby minimizing any erratic flow in the fluid injection system. Inanother example, the first fluid 30 may be more viscous than the secondfluid 32. In this example, the process described above in reference toFIG. 7, would be switched to apply a proportionally larger pressure tothe second fluid 32 in comparison to the pressure applied to the firstfluid 30. It is also contemplated that the first fluid 30 and the secondfluid 32 may have substantially equal viscosities. In this example,equal pressures may be applied to the first fluid 30 and the secondfluid 32 at the outset. For example, in certain embodiments a moreviscous fluid may be diluted with a less viscous fluid, or vice versa,so that the 4-Viscosity between the two injected fluids is minimized4-Viscosity may also be reduced by heating a fluid having a higherviscosity, for example to a temperature close to body temperature, priorto the injection procedure.

In another example, after pressure has been applied to the first fluid30 and the second fluid 32, the flow rate of each fluid 30, 32 ismeasured. In the event the flow rates are not equal to one another, thefluid injection system may pause or hold the injection procedure, orpause injection or one or both fluids, to allow both fluids 30, 32 toachieve a steady-state pressure to reduce any stored energy in the fluidinjection system. In one example, as the flow rates of the fluids 30, 32are being measured, in the event it is determined that the flow rate offirst fluid 30 is not equal to the flow rate of the second fluid 32 thefluid injection system can pause or hold the injection procedure whilepressure is applied to either the first fluid 30 or the second fluid 32to equalize the flow rates of the fluids 30, 32. In another example, theoverall flow rate of the fluid exiting the catheter is measured duringthe injection procedure. The information regarding the overall flow rateis sent as real-time feedback information to the controller 38 to permitthe controller 38 to adjust the pressures applied to the first fluid 30and/or second fluid 32 to equalize the flow rates through the fluidinjection system to ensure a consistent overall flow of fluid is exitingfrom the catheter into the patient's blood vessel. As shown in FIG. 37,in one example, a sensor 300, for example an ultrasonic mass flow ratesensor or other suitable flow rate sensor, is used to measure theoverall flow rate in real-time of at least one of the first fluid 30 andsecond fluid 32 through the system. It is contemplated that the sensor300 can be placed a various positions within the system. It is alsocontemplated that more than one sensor 300 is used to measure theoverall flow rate of at least one of the first fluid 30 and the secondfluid 32 at different positions in the system. In one example, thesensor 300 is a sensor that clips onto the exterior of the fluid pathset 112 to the catheter. In another embodiment, the flow rate sensor maybe internal and located within the fluid flow path. It is contemplated,however, that other flow rate sensing technologies could be used andalternative mounting scenarios could be used to position the sensor 300on the fluid path set 112. The sensor 300 provides a real-time feedbackloop to the controller 38 to control one or more of the injectionparameters based on the overall flow rate measured by the sensor 300. Inother embodiments, such a sensor arrangement could also be used withperistaltic systems and other continuous flow injector systems. Inanother example, an air sensor 310 is provided in line with the sensor300 to measure the air content in the fluid flowing through the fluidpath set 112. The information measured by the air sensor 310 may also befed back to the controller 38 to control one or more of the injectionparameters. For example, pressure applied to a plunger for a firstviscous fluid 30 may be ramped down and pressure applied to a plunger ofa second less viscous fluid 20 may be ramped up or one or more otherfluid injection parameters may adjusted as appropriate so that thereal-time feedback from a flow sensor indicates that the flow rate ofthe fluid exiting a catheter is substantially constant, for example notvarying by more than 2.0 mL/sec, 1.5 mL/sec, 1.0 mL/sec, 0.5 mL/sec,0.25 mL/sec, or even 0.1 mL/sec during transition from the first fluid30 to the second fluid 20.

As further shown in FIG. 7, a check valve 40 may also be provided in thefluid injection system. The check valve 40 may be positioned in-linewith the tubing of the first fluid 30. Using this check valve 40, thefirst fluid 30 will only flow into the second fluid 32 flow until apredetermined pressure is achieved by the first fluid 30. Thepredetermined pressure may be substantially equal to the desired flowrate pressure of the second fluid 32. The check valve 40 may be chosenbased on the desired predetermined pressure. With the use of the checkvalve 40, the second fluid 32 is not permitted to flow back into thetubing of the first fluid 30, thereby reducing the expansion of thesecond fluid 32 syringe and/or first fluid 30 syringe under the extrapressure. In the example where the first fluid 30 is less viscous thanthe second fluid 32, the check valve 40 may be positioned in-line withthe tubing of the first fluid 30 to prevent the first fluid 30 fromopening the check valve 40 until a predetermined pressure has beenapplied to the first fluid 30. According to this example, capacitancebuild up in the first syringe 30 is reduced by eliminating any componentfrom the pressure applied to the second fluid 32.

In a similar fashion, as shown in FIG. 8, a check valve 42 may beprovided in-line with the tubing of the second fluid 32 portion of thefluid injection system. Similar to the check valve 40 on the first fluid30 portion, the check valve 42 may be configured to control the flow ofthe second fluid 32 through the fluid injection system based on adesired predetermined pressure for the fluid injection system. The checkvalve 42 may be chosen according to the desired predetermined pressure.Using this system and method, the controller 38 may control the amountof pressure applied to the first fluid 30 and the second fluid 32 viathe motors 35, 37 and plungers 34, 36. The controller 38 may monitor thepressures of the first fluid 30 and the second fluid 32 and adjust theplungers 34, 36 accordingly to maintain equal pressures in the fluidinjection system. Using the check valve 42 on the second fluid 32portion of the fluid injection system, the peak pressure values in thefluid injection system can be significantly lowered. Using thisarrangement, the pressure of the first fluid 30 can reach apredetermined pressure, while the check valve 42 does not release thesecond fluid 32 until the predetermined pressure on the second fluid 32is also achieved, thereby reducing the amount of second fluid 32 thatbackflows into the first fluid 30 portion of the fluid injection system.In one example, the first fluid 30 may be brought to the predeterminedpressure and then the second fluid 32 may be subsequently pressurized tobe released through the check valve 42. It is contemplated that thecontroller 38 can be programmed to initiate these pressurizationprocedures. In the example where the first fluid 30 is more viscous thanthe second fluid 32, the check valve 42 may be positioned in-line withthe tubing of the second fluid 32 to prevent the second fluid 32 fromopening the check valve 42 until a predetermined pressure has beenapplied to the second fluid 32.

As shown in FIG. 9, it is also contemplated that the fluid injectionsystem may include a check valve 40 on the first fluid 30 portion of thefluid injection system and a check valve 42 on the second fluid 32portion of the fluid injection system. In this arrangement of the fluidinjection system, fluid pressure from the non-active portion of thefluid injection system may be eliminated or isolated until the activeportion of the fluid injection system reaches the same fluid pressure.For example, fluid pressure from the second fluid 32 may be eliminatedor isolated in the fluid injection system until the fluid pressure ofthe first fluid 30 reaches a predetermined pressure or an equal pressureto the second fluid 32. The check valves 40, 42 may be chosen based onthe desired predetermined pressure of the first fluid 30 and the secondfluid 32. Using this arrangement, the first fluid 30 and the secondfluid 32 are not mixed together in the fluid injection system until eachfluid has reached the predetermined fluid pressure. A controller 38 mayalso be used in this arrangement to control the pair of motors 35, 37that actuate the plungers 34, 36 that apply pressure to the first fluid30 and the second fluid 32. The controller 38 may be pre-programmed withinformation regarding the threshold pressures for the check valves 40,42, and user input on information on the first fluid 30 and second fluid32 may be used to coordinate the proper pressures applied by theplungers 34, 36 to the first fluid 30 and the second fluid 32. Inanother example, the check valves 40, 42 may be high crack pressurecheck valves configured to reduce or essentially eliminate the backflowin the fluid injection system. The high crack pressure check valves 40,42 may be check valves that allow flow in one direction with arelatively low pressure drop. The high crack pressure check valves 40,42 may have a high opening or cracking pressure that may be above ornear the maximum operating pressure of the fluid injection system. Oneexample of such a high cracking pressure valve may include a spool valvehaving an internal sliding element that can block fluid flow. The valvemay include a resistive force element, such as a spring or a pressurizedbladder, to resist the movement of the sliding element. By providing thehigh crack pressure check valves 40, 42 with a high cracking pressure,no fluid may continue to flow or dribble out of the two syringes intothe fluid path and possibly the patient until the requisite pressurebalance is achieved in the fluid injection system. In another example,the open position of the check valves 40, 42 can be adjusted so that thecheck valves 40, 42 are partially open to control the flow of fluidthrough the check valves 40, 42. The check valves 40, 42 may be adjustedmanually or automatically by the controller 38. Based on the flow ratesof the first fluid 30 and/or the second fluid 32, the check valves 40,42 can be partially opened, fully opened, or closed to achieve a desiredflow rate of the fluid 30, 32 through the check valve 40, 42.

As shown in FIGS. 10 and 11, another method of reducing undesired spikesin fluid flow rates in and providing accurate fluid mixing ratios to thepatient is through the use of an over-travel and fast-controlled reversepull of the plunger 34 within the first fluid 30 syringe to at leastpartially compensate for any undelivered first fluid 30 in the fluidinjection system due to capacitance volume of the system. In thisarrangement, the second fluid 32 may be more viscous than the firstfluid 30. The over-travel position and fast-controlled reverse pull ofthe plunger 34 may be calculated according to the amount of potentialstored volume in the first fluid 30 syringe based on the desired fluidpressure and the plunger 34 position at the end of the first fluid 30injection procedure. To determine the length of over-travel for theplunger 34 needed to receive the desired volume of the first fluid 30,the following equation is used to calculate the plunger 34 over-traveldistance, as identified in U.S. Patent Application Publication No.2010/0222768 to Spohn et al., which is hereby incorporated by referencein its entirety:Over Travel (mL)=C ₁ +C ₂ *x+C ₃ *x ^(Λ2)+C₄ *x ^(Λ3) +C ₅ *y+C ₆ *y^(Λ2) +C ₇ *y ^(Λ3)

-   -   (Where: C₁=−0.811; C₂=0.039; C₃=−0.00035; C₄=9.05E-7; C₅=0.0269;        C₆=−4.43e-5; C₇=2.607e-8; x axis=pressure; y axis=position)

To receive the desired volume of the first fluid 30 from the fluidinjection system, the plunger 34 must be over-traveled the same amountand then the plunger 34 is pulled back in reverse to compensate forrelease of the capacitance volume of the first fluid 30 syringe.

With reference to FIG. 10, upon activation of the controller 38, themotor 35 is activated to drive the plunger 34, which causes transitionof the plunger 34 from a first initial position P1 _(plunger) (shown indashed lines) to a second extended position P2 _(plunger), therebyadvancing the plunger 34 a corresponding delivery distance D1_(plunger). As the plunger 34 is transitioned across the deliverydistance D1 _(plunger), a pre-set volume of the first fluid 30 isdelivered from the interior of the first fluid 30 syringe to adownstream location. During delivery of the first fluid 30 from theinterior of the syringe to the downstream location, the syringe swellsand the system otherwise increases in capacitance volume as describedherein, in such a manner that it is radially displaced from its initialconfiguration. As the plunger 34 is advanced longitudinally within thesyringe to dispel liquid from the interior of the syringe, the firstfluid 30 imparts an axial force to the wall of the syringe.

As shown in FIG. 11, in order to account for the under-delivery of fluidfrom the interior of the syringe due to the swelling of the syringe andother capacitance effects, the plunger 34 can be programmed toover-travel a sufficient longitudinal distance to compensate for systemcapacitance, such as the expansion of the syringe when under resultingaxial pressure. In order to over-travel a specified longitudinaldistance, the motor 35 is actuated by the controller 38, which causesfurther transition of the plunger 34 from the second extended positionP2 _(plunger) (shown in dashed lines) to a third over-travel position P3_(plunger), thereby advancing the plunger 34 a corresponding deliverydistance D2 _(plunger). As the plunger 34 is transitioned across thedelivery distance D2 _(plunger), a pre-determined volume of the firstfluid 30 is delivered from the interior of the syringe to the downstreamlocation to compensate for the under-delivery of fluid from the interiorof the syringe as a result of the capacitance volume of the first fluid30 syringe during transition from the first initial position to thesecond extended position.

Once forward longitudinal movement of the plunger 34 within the syringeis ceased, the plunger 34 may be rapidly driven back in order tocompensate for the increased pressures within the fluid injection systemresulting from the over-travel of the plunger 34. In order for theplunger 34 to retract to the retracted position, the controller 38activates the motor 35, which causes transition of the plunger 34 fromthe third over-travel position P3 _(plunger) to the retracted position,thereby retracting the plunger 34 a corresponding retraction distance.This rapid backwards retraction of the plunger 34 relieves the swellingof the syringe and depressurizes the system. In one example, the rapidback-drive of the plunger 34 can be on the order of about 20 mL/s to 30mL/s, for example 25 mL/s. This depressurization of the system allowsthe linear travel of the plunger 34 to coincide with the actualcommanded location, irrespective of capacitance volume. In the examplewhere the first fluid 30 is more viscous than the second fluid 32, theprocess described above in reference to FIGS. 10 and 11 would beswitched to apply an over-travel and fast-controlled reverse pull of theplunger 36 within the second fluid 32 syringe to compensate for anyundelivered second fluid 32 in the fluid injection system. It is alsocontemplated that the first fluid 30 and the second fluid 32 may havesubstantially equal viscosities. In this example, equal pressures may beapplied to the first fluid 30 and the second fluid 32 at the outset ofthe process.

In typical fluid injection systems with saline and contrast mediumfluids, the contrast medium has a higher viscosity than the saline. Dueto this difference in viscosity, it is often difficult to apply thecorrect pressure to each fluid to achieve a uniform pressure between thetwo fluids to create a smooth flow of the mixture of the two fluids tothe downstream location or sequential flow of the fluids without a flowspike at the fluid transition. As described herein, the higher viscosityof the contrast medium may cause backflow in the fluid injection systemand/or swelling of the syringes holding the saline and/or contrastmedium. Therefore, in one embodiment of the disclosure, the saline usedin the fluid injection system may be replaced with an alternative fluidthat has similar properties to saline but has a higher viscosity tosubstantially match the higher viscosity of the contrast medium. In oneexample, the saline may be replaced with a Ringers Lactate solution,which has a viscosity similar to blood or low viscosity contrastmediums. The pressure required to deliver the Ringers Lactate solutionthrough the fluid injection system is higher than saline, which leads toa smaller difference between the pressure to move the Ringers Lactatesolution and that needed to move the more viscous contrast mediumresulting in lower spikes or jumps in the flow rates of the two fluids.The Ringers Lactate solution will also have a higher density thansaline, which will reduce the density exchange between the RingersLactate solution and the contrast medium.

As shown in FIG. 12, in another example of the present disclosure, thesecond fluid 32 syringe may be designed with a lower capacitance (storedvolume under pressure) than conventional syringes to reduce the effectof backflow into the second fluid 32 syringe. In one embodiment, thefirst fluid 30 may be more viscous than the second fluid 32. In anembodiment, a pressure jacket 44 may be provided around the outersurface of at least the second fluid 32 syringe to restrict the swellingin at least the second fluid 32 syringe due to backflow of second fluid32. By providing the pressure jacket 44, the outer circumferentialsurface of the second fluid 32 syringe is reinforced, thereby limitingthe amount of expansion or swelling in the second fluid 32 syringe. Thepressure jacket 44 is configured to lower the capacitance of the secondfluid 32 syringe, which results in a more accurate volume of the secondfluid 32 being provided at the downstream location. The pressure jacket44 may be made from a hard, medical-grade plastic, composite, or metalto provide the sufficient rigidity to the second fluid 32 syringe. It isalso contemplated that an additional pressure jacket 46 may be providedaround the outer circumferential surface of the first fluid 30 syringe.The pressure jacket 46 will assist in also lowering the capacitance ofthe first fluid 30 syringe, thereby providing more accurate volumes ofthe first fluid 30 at the downstream location. In the example where thesecond fluid 32 is more viscous than the first fluid 30, the pressurejacket 44 may be provided on the first fluid 30 syringe and theadditional pressure jacket 46 may be provided on the second fluid 32syringe.

With reference to FIGS. 13-15, additional methods for reducing undesiredspikes in fluid flow rates in the fluid injection system are described.In FIGS. 13 and 14, an obstruction member 48 may be provided in thesecond fluid 32 syringe to increase the fluid pressure of the secondfluid 32 through the second fluid 32 syringe. In this example, the firstfluid 30 may be more viscous than the second fluid 32. In one example,the obstruction member 48 may include an opening 50 configured toincrease the fluid pressure of the second fluid 32 based on the desiredfluid pressure through the fluid injection system. In one example, theopening 50 may be circular. However, it is contemplated that alternativeshapes for the opening may be used, along with additional openings inthe obstruction member 48. The obstruction member 48 is configured toincrease the fluid pressure of the second fluid 32 so the second fluid32 tubing of the fluid injection system does not decompress during thefluid injection process. Further, the increased fluid pressure of thesecond fluid 32 will decrease the amount of backflow that is directed tothe second fluid 32 syringe, which may expand or swell the second fluid32 syringe. The increased pressure of the second fluid 32 may besubstantially equal to the pressure of the first fluid 30. In theexample where the second fluid 32 is more viscous than the first fluid30, the obstruction member 48 may be provided in the first fluid 30syringe to increase the fluid pressure of the first fluid 30 through thefirst fluid 30 syringe.

Similar to the obstruction member 48 used in FIGS. 13 and 14 to obstructthe flow of the second fluid 32 through the second fluid 32 syringe, inanother example of the disclosure the second fluid 32 syringe mayinclude a reduced inner diameter to create a similar obstruction. Asshown in FIG. 15, the inner diameter of the second fluid 32 syringe hasbeen reduced from a larger diameter (shown in dashed lines) to a smallerdiameter to increase the fluid pressure of the second fluid 32 throughthe fluid injection system. The inner diameter of the second fluid 32syringe may be reduced in only a portion of the second fluid 32 syringeor the inner diameter of the second fluid 32 syringe may be reducedalong the entire length of the second fluid 32 syringe. Similar to theobstruction member 48, the reduced inner diameter of the second fluid 32syringe is configured to increase the fluid pressure of the second fluid32 so the second fluid 32 tubing of the fluid injection system does notdecompress during the fluid injection process. Further, the increasedfluid pressure of the second fluid 32 will decrease the amount ofbackflow that is directed to the second fluid 32 syringe, which mayresult in the expansion or swelling of the second fluid 32 syringe. Thereduced inner diameter will also assist in bringing the pressure of thesecond fluid 32 to a substantially equal pressure as the first fluid 30.In the example where the second fluid 32 is more viscous than the firstfluid 30, the inner diameter of the first fluid 30 syringe may bereduced to create a similar obstruction.

With reference to FIG. 16, another method of reducing undesired spikesin fluid flow rates is described. In this example, the first fluid 30may be more viscous than the second fluid 32. In this example, anexternal restriction member 52 may be provided around at least a portionof the outer circumferential surface of the second fluid 32 syringe. Theexternal restriction member 52 may be cylindrical in shape. However, itis contemplated that alternative shapes and sizes may be used with thesecond fluid 32 syringe. The external restriction member 52 may definean aperture through which the second fluid 32 syringe may be inserted.The external restriction member 52 may be provided via a friction-fit onthe second fluid 32 syringe to control the flow rate of the second fluid32 through the second fluid 32 syringe. The external restriction member52 may reduce the swelling or expansion of the second fluid 32 syringedue to any backflow into the second fluid 32 syringe, thereby reducingthe capacitance of the second fluid 32 syringe. The external restrictionmember 52 may apply pressure to the outer surface of the second fluid 32syringe, thereby restricting the flow of the second fluid 32 through thesecond fluid 32 syringe. Pressure may be applied by the externalrestriction member 52 by decreasing the diameter of the aperture definedby the external restriction member 52. It is also contemplated that thepressure applied by the external restriction member 52 may be controlledby the controller 38. The controller 38 may be programmed to adjust thepressure applied by the external restriction member 52 and the diametersize of the aperture defined by the external restriction member 52 basedon the fluid pressures in the fluid injection system, the capacitance ofthe second fluid 32 syringe and the first fluid 30 syringe, the cathetersize, and the viscosities of the second fluid 32 and the first fluid 30,among other factors. The controller 38 may also be programmed to adjustthe diameter size of the aperture defined by the external restrictionmember 52 based on the timing of the fluid injection procedure. In theexample where the second fluid 32 is more viscous than the first fluid30, the external restriction member 52 may be provided around a portionof the outer circumferential surface of the first fluid 30 syringe.

With reference to FIG. 17, another method of reducing undesired spikesin fluid flow rates is described. In this example, the second fluid 32may be more viscous than the first fluid 30. This method includes theuse of an equalizing flow valve 56 to monitor and control the flow ratesof the first fluid 30 and the second fluid 32. The equalizing flow valve56 may be positioned in the fluid injection system at a location wherethe first fluid 30 tubing and the second fluid 32 tubing connect withone another. The equalizing flow valve 56 may monitor the flow rates ofthe first fluid 30 and the second fluid 32 and adjust an orifice definedby the equalizing flow valve 56 to maintain the desired delivery flowrates of the two fluids. In one example, the equalizing flow valve 56may be connected to a controller 38, which also actuates the motors 35,37 that drive the plungers 34, 36 in the fluid injection system based onreal-time feedback readings from equalizing flow valve 56. Using thecontroller 38 with the equalizing flow valve 56, the pressure applied bythe plungers 34, 36 can be adjusted according to the flow rates of thetwo fluids through the equalizing flow valve 56. The controller 38 maybe programmed to read the flow rates of the two fluids through theequalizing flow valve 56 and adjust the pressure applied by the plungers34, 36 accordingly to ensure that the second fluid 32 and the firstfluid 30 have substantially equal pressures. Alternatively, thecontroller 38 and/or equalizing flow valve 56 may be pre-programmedaccording to the types of fluids used in the fluid injection system,fluid volumes, syringe features, catheter size, the capacitance of thefluid injection system, and/or the desired flow rates of the two fluids,which information may be stored in the controller 38. An operator maymanually input the information regarding the fluid injection system intothe controller 38, which will assist in adjusting the plunger 34, 36pressure and/or the equalizing flow valve 56 accordingly to obtain thedesired flow rates of the two fluids.

With reference to FIG. 18, another method of reducing undesired spikesin fluid flow rates is described. In this example, the first fluid 30may be more viscous than the second fluid 32. According to thisembodiment, during operation of the fluid injection system, an operatorwill likely know the pressures that are to be applied by the plungers34, 36 and the volume of the first fluid 30 and the second fluid 32 inthe fluid injection system. By determining the capacitance of the secondfluid 32 syringe, the operator can adjust the plunger 36 of the secondfluid 32 syringe accordingly to account for the extra stored volume ofthe second fluid 32 due to the capacitance of the second fluid 32syringe. Using this method, the plunger 36 may be pulled back from thesecond fluid 32 syringe equal to a capacitance volume of the secondfluid 32 syringe, which will reduce the pressure to zero in the secondfluid 32 syringe. The second fluid 32 may then be injected at thedesired flow rate without experiencing any swelling or expansion in thesecond fluid 32 syringe. It is also contemplated that the plunger 36 maybe pulled back by an instruction from the controller 38. Based oninformation regarding the fluid injection system, such as, fluidviscosities, catheter size, capacitance of the second fluid 32 syringe,and/or the volume of fluid in the fluid injection system, the controller38 may be programmed to pull the plunger 36 from the second fluid 32syringe in an amount equal to the capacitance volume of the second fluid32 syringe. For example, if the second fluid 32 syringe capacitance is10 mL, the plunger 32 may be pulled from a starting position P1 (shownin dashed lines) to a new position P2 to compensate for the extra volumethat will be stored in the second fluid 32 syringe during the fluidinjection procedure. In the example where the second fluid 32 is moreviscous than the first fluid 30, the process described above withreference to FIG. 18 may be used with the first fluid 30 syringe.

According to an embodiment, in a similar method, a test injectionprocedure using the first fluid 30 and second fluid 32 may be performedbefore the actual diagnostic phase, using the same flow rates as will beused from the diagnostic injection procedure. A pressure measurement ofthe first fluid 30 phase is obtained during the test injectionprocedure, which gives an indication of the expected pressure for theprogrammed flow rate under the current tubing and patient conditions.This measured pressure value is recorded and used during the diagnosticinjection procedure to modify the flow rate of at least one of the firstfluid 30 and the second fluid 32 to modify the flow rate and fluid flowprofile of at least one of the first fluid 30 and the second fluid 32 tocompensate for capacitance in the injector system. In one example, theflow rate modification is achieved by temporarily changing a pressurelimit of one of the fluids 30, 32 in an adaptive flow algorithm used bya controller 38 to control the pressures of the fluid injection system.In another embodiment, a series of flow algorithms may be programmedinto a controller 38 or processor based on set of pre-programmedinjection protocols. Alternatively, one or more algorithms may bedetermined and programmed into the controller 38 that utilize varioussystem parameters for a specific injection setup and protocol, such as,for example, fluid volumes and types, temperature, syringe volumes andtypes, desired flow rates, target organ or body part for imaging,patient information, etc., where the algorithms utilize the variousparameters to calculate and appropriate injection protocol for theinjection procedure.

With reference to FIGS. 28 and 29, another embodiment of a method ofproviding more accurate mixing ratios is described. During currentmulti-fluid injection procedures, a spike in saline flow rate may occurwhen the fluid passing through the catheter suddenly changes inviscosity, for example during a transition from contrast to saline,resulting in a drop in the pressure at the restriction point of thecatheter. During this period of pressure drop, any fluid stored in thecompliance of a disposable set or system capacitance holding the fluidis released through the catheter. As shown in FIG. 28, contrast mediumis initially directed through the catheter. After the contrast mediumhas been injected, the saline is injected and begins to flow through thecatheter. A transition period occurs when the flow rate of the contrastmedium begins to decrease through the catheter and the flow rate of thesaline begins to increase through the catheter. During this transitionperiod, the viscosity of the fluid flowing through the catheter suddenlyand quickly changes, which results in a spike of the saline flow ratethrough the catheter. Due to the short transition period that occursduring the switch between injecting the contrast medium and injectingthe saline, an increased drop in pressure is created, which causes anincreased saline flow rate spike in the fluid exiting the catheter.

As shown in one embodiment in FIG. 29, by extending the transitionperiod between injecting the contrast medium and injecting the saline, amore gradual viscosity/pressure gradient may be achieved during theinjection procedure. With this extended transition period, the samevolume of fluid is released over a longer period of time, so the averageflow rate magnitude of the saline spike is reduced. The flow rate of thecontrast medium is gradually and slowly reduced, while the flow rate ofsaline is gradually and slowly increased. The change in viscosity of thefluid through the catheter is gradual, resulting in a decreased drop ofthe pressure in the catheter. The extended transition period may beachieved in such a manner that does not increase the volume of contrastmedium that is delivered during the injection procedure and does notdegrade the efficacy of the injection procedure. It is also contemplatedthat non-linear or non-continuous extended transition periods could beused, which would result in less impact to the image taken of thepatient, and taking advantage of the fluid dynamics of the fluidinjection system. In other embodiments, real-time fluid flow ratemeasurements in a feedback loop to a processor may allow the processorto adjust the contrast and saline flow rates appropriately to minimizeany spike in fluid flow rate during transition from one fluid toanother.

In another example, the viscosity of the first fluid 30 or the secondfluid 32 is adjusted to minimize or dampen the spike or increase in theoverall flow rate during a transition between delivering one of thefirst fluid 30 and the second fluid 32 to delivering the other of thefirst fluid 30 and the second fluid 32. In one example, a volume of thefirst fluid 30 is added to the second fluid 32 to dilute the overallviscosity of the second fluid 32. Since the first fluid 30 has a lowerviscosity, the first fluid 30 will dilute the second fluid 32 and reducethe overall viscosity of the second fluid 32. In another example, theviscosity of the first fluid 32 is increased to match the viscosity ofthe second fluid 32. By equalizing the viscosities of the fluids 30, 32,the transition of flow between the delivery of one of the first fluid 30and the second fluid 32 and the delivery of the other of the first fluid30 and the second fluid 32 does not create such a large spike orincrease in the overall flow rate exiting from the catheter.

B. Solutions for Reducing Catheter Kickback and Rapid Movement

With reference to FIGS. 19-27, several methods are described forreducing undesired spikes in fluid flow rates by using several differentcatheter designs to control the erratic flow of fluid to the patient'sblood vessel. The following methods are configured to reduce the amountof kick-back or pull out the catheter experiences when the erratic flowof the contrast medium is delivered through the fluid injection system.

As shown in FIG. 19, one method of reducing kick-back in the catheter 60is to provide a rigid member 62 along the longitudinal length of thecatheter 60. In one example, the rigid member 62 may be a wire. Therigid member 62 may be attached to the outer surface of the catheter 60or embedded in the walls of the catheter 60. The rigid member 62 may beconfigured to stiffen the catheter 60 from bending during injection ofthe erratic fluid from the fluid injection system. By stiffening thecatheter 60 with the rigid member 62, the catheter 60 may be less likelyto kick-back or pull out of the injection site when the erratic flow isdelivered through the catheter 60. By reducing the kick-back of thecatheter 60, the catheter 60 may be less likely to extend into thesurrounding tissue of the patient.

As shown in FIGS. 20A and 20B, another method of reducing kick-back inthe catheter 60 is to provide a sheath or braided member 63 on an outercircumferential surface of the catheter 60. The sheath 63 may extendalong the length of the catheter 60 or may only be provided on a distalend of the catheter 60. In one example, the inner diameter of the sheath63 may be substantially equal to the outer diameter of the catheter 60so that the catheter 60 may fit within the sheath 63. The sheath 63 maybe made of stainless steel wire interlaced together, nylon, Kevlar,spectra fiber, or any other suitably flexible material that is safe toinsert into a patient's blood vessel. Initially, before injection offluid through the catheter 60, the sheath 63 and catheter 60 aresubstantially deflated within the patient's blood vessel (FIG. 20A). Asfluid is injected through the catheter 60, the fluid expands the innerdiameter of the catheter 60 to permit fluid to flow therethrough (FIG.20B). As the catheter 60 expands against the inner diameter of thesheath 63, the sheath 63 also begins to expand. The catheter 60 expandsuntil the catheter 60 and the sheath 63 have expanded to theirrespective maximum outer diameters. The outer diameter of the sheath 63may be substantially equal to an inner diameter of at least a portion ofa blood vessel so that the outer diameter of the catheter 60 isconstrained by the sheath 63 to keep the catheter 60 from expanding to adiameter larger than the diameter of a blood vessel. By keeping theouter diameter of the catheter 60 smaller than the blood vessel, thefluid exiting the catheter 60 remains coaxial with the catheter 60.Since the inner diameter of the catheter 60 expands slowly underpressure when initially deflated, the jetting velocity and accelerationof the fluid through the catheter 60 is reduced, which also reduces anykick-back or rapid movement of the catheter 60 in the patient's bloodvessel. Further, as sheath 63 expands against the inner wall of at leasta portion of the patient's blood vessel, the sheath 63 may be secured tothe inner walls to stabilize catheter 60 within the blood vessel or mayseal the needle hole entrance in the blood vessel, thereby reducing therisk of rapid movement of the catheter.

As shown in FIGS. 21 and 22, another method of reducing kick-back in thecatheter 60 is to provide a split tip 64 on the distal end of thecatheter 60. The split tip 64 may define an aperture 66 through whichthe fluid may be delivered to the patient. As shown in FIG. 21, thesplit tip 64 may be configured to remain in a closed position in whichthe aperture 66 also remains closed. In this example, the split tip 64will not open until a predetermined or sufficient pressure is providedby the fluid in the catheter 60. With reference to FIG. 22, uponreaching this predetermined pressure, the aperture 66 of the split tip64 will open and allow the fluid to be delivered into the patient'svein. The split tip 64 assists in reducing the erratic flow of the fluidthat is permitted to exit from the catheter 60. The fluid is unable toexit into the patient's vein until the predetermined pressure isachieved, which stabilizes the fluid in the catheter 60 before injectioninto the patient. It is also contemplated that different shapes andnumber of apertures in the split tip 64 may be utilized to improve thestability of the catheter 60.

As shown in FIGS. 23 and 24, similar to the split tip 64 of FIGS. 21 and22, another method of reducing kick-back in the catheter 60 includesproviding an over-molded tip 68 on the distal end of the catheter 60.The over-molded tip 68 may be configured to overlap the distal end ofthe catheter 60. The over-molded tip 68 may be configured to open andallow the fluid to exit the distal end of the catheter 60 upon the fluidreaching a predetermined or threshold pressure. As shown in FIG. 23, theover-molded tip 68 is configured to remain closed during use of thecatheter 60, until a certain pressure is obtained by the fluid. Once thefluid pressure has increased to the threshold pressure, the over-moldedtip 68 will open and move away from the opening of the distal end of thecatheter 60 (as shown in FIG. 24), thereby permitting the fluid to exitinto the patient's blood vessel. The over-molded tip 68 assists inreducing the erratic flow of the fluid that is permitted to exit fromthe catheter 60. The fluid is unable to exit into the patient's veinuntil the predetermined pressure is achieved, which stabilizes the fluidin the catheter 60 before injection into the patient. It is alsocontemplated that different shapes of the over-molded tip 68 may beutilized to improve the stability of the catheter 60.

With reference to FIG. 25, another method of reducing kick-back in thecatheter 60 includes tapering the inside diameter of the catheter 60 toallow more steady flow of fluid through the catheter 60. In one example,the inner diameter may start at a smaller dimension at a proximal end 70of the catheter 60. In this example, the inner diameter will taper orincrease outwardly to the distal end 72 of the catheter 60, which willhave a larger inner diameter than the proximal end 70. By tapering theinner diameter in this fashion such that the proximal end has a smallerdiameter, a reduction in the proximal hoop stress on the catheter 60tubing at the proximal end 70 of the catheter 60 is achieved, and areduction in the kick-back or rapid movement of the catheter 60 bylowering the acceleration of the fluid as it exits the catheter 60 maybe achieved. It is contemplated that the catheter 60 may begin to taperat different locations along the length of the catheter 60. However,proximal end 70 of the catheter 60 will always have a smaller innerdiameter than the distal end 72 of catheter 60. It is contemplated thatthe dimensions of the inner diameter at proximal end 70 and distal end72 may vary in catheter 60.

With reference to FIGS. 26 and 27, another method of reducing kick-backin the catheter 60 includes providing a balloon tip 74 on an end of thecatheter 60. The balloon tip 74 may be made from a flexible material sothe balloon tip 74 can be stretched. The balloon tip 74 may beinflatable and deflatable based on the amount of fluid that is directedthrough the balloon tip 74. The balloon tip 74 may be provided on thedistal end 72 of the catheter 60. As shown in FIG. 26, when fluid is notbeing provided through the catheter 60, the balloon tip 74 is deflatedand rests in the blood vessel 76 of the patient on the distal end 72 ofthe catheter 60. As shown in FIG. 27, upon fluid being injected throughthe catheter 60, the balloon tip 74 is inflated by the liquid and isdirected out of the balloon tip 74 via an aperture 78. When fluid isdirected through the balloon tip 74, the balloon tip 74 is expanded tosubstantially the same inner diameter size as the blood vessel 76. Theballoon tip 74 may assist in centering the flow of the liquid throughthe blood vessel 76. The balloon tip 74 may also anchor the catheter 60to the inner walls of the blood vessel 76 to seal any puncture holes inthe blood vessel 76 from leaking any injected fluid into the surroundingtissue. This sealing feature is particularly advantageous when thecatheter 60 punctures through both walls of the blood vessel 76 and isthen slightly pulled back into the blood vessel 76. The balloon tip 74will assist in sealing any accidental punctures in the blood vessel 76walls to reduce any contrast medium or saline leaking into thesurrounding tissue.

While several examples of a fluid injection system and catheter areshown in the accompanying figures and described hereinabove in detail,other examples will be apparent to, and readily made by, those skilledin the art without departing from the scope and spirit of thedisclosure. For example, it is to be understood that this disclosurecontemplates that, to the extent possible, one or more features of anyexample can be combined with one or more features of any other example.Accordingly, the foregoing description is intended to be illustrativerather than restrictive.

What is claimed is:
 1. A method of maintaining an overall flow rateduring a sequential delivery of at least two fluids to a patient's bloodvessel, the method comprising: delivering at least a first fluid intothe patient's blood vessel at a first flow rate; delivering at least asecond fluid into the patient's blood vessel at a second flow rate; andadjusting at least one of a first flow profile of the first flow rateand a second flow profile of the second flow rate to dampen a transientincrease in the overall flow rate during a transition between deliveringone of the first fluid and the second fluid to delivering the other ofthe first fluid and the second fluid.
 2. The method of claim 1, whereinadjusting at least one of the first flow profile of the first flow rateand a second flow profile of the second flow rate comprises delaying adelivery of one of the first fluid and the second fluid until the otherof the first fluid and the second fluid reaches a predetermined flowrate.
 3. The method of claim 1, wherein adjusting at least one of thefirst flow profile of the first flow rate and a second flow profile ofthe second flow rate comprises adjusting one of the first flow rate andthe second flow rate using a controller, wherein the adjusting is basedon the other of the first flow rate and the second flow rate.
 4. Themethod of claim 1, further comprising pressurizing the first fluid usinga first check valve to a first predetermined pressure before deliveringthe first fluid.
 5. The method of claim 1, further comprisingpressurizing the second fluid using a second check valve to a secondpredetermined pressure before delivering the second fluid.
 6. The methodof claim 1, further comprising pressurizing the first fluid and thesecond fluid using a first check valve and a second check valve to afirst predetermined pressure and a second predetermined pressure,respectively, before delivering the first fluid and the second fluid. 7.The method of claim 1, wherein adjusting at least one of the first flowprofile of the first flow rate and a second flow profile of the secondflow rate comprises over-delivering a predetermined volume of at leastone of the first fluid and the second fluid during the delivery of theat least one of the first fluid and the second fluid.
 8. The method ofclaim 1, further comprising diluting one of the first fluid and thesecond fluid with a predetermined volume of the other of the first fluidand the second fluid.
 9. The method of claim 1, further comprising:providing a multi-fluid injection system comprising: a first syringe forreceiving the first fluid and a first plunger movable within a barrel ofthe first syringe to pressurize the first fluid for delivery to thepatient's blood vessel; and a second syringe for receiving the secondfluid and a second plunger movable within a barrel of the second syringeto pressurize the second fluid for delivery to the patient's bloodvessel; and reducing a capacitance of at least one of the first syringeand the second syringe to prevent backflow of at least one of the secondfluid into the first syringe and the first fluid into the secondsyringe.
 10. The method of claim 9, further comprising providing apressure jacket around an outer circumference of at least one of thefirst syringe and the second syringe to reduce the capacitance of the atleast one of the first syringe and the second syringe when the at leastone of the first syringe and the second syringe is under pressure. 11.The method of claim 1, further comprising: providing a multi-fluidinjection system comprising: a first syringe for receiving the firstfluid and a first plunger movable within a barrel of the first syringeto pressurize the first fluid for delivery to the patient's bloodvessel; and a second syringe for receiving the second fluid and a secondplunger movable within a barrel of the second syringe to pressurize thesecond fluid for delivery to the patient's blood vessel, wherein atleast one of the first syringe and the second syringe includes a reducedinner diameter to correspond to a desired flow rate.
 12. The method ofclaim 11, further comprising providing an obstruction member within atleast one of the first syringe and the second syringe to reduce theinner diameter of at least one of the first syringe and the secondsyringe.
 13. The method of claim 1, further comprising: providing amulti-fluid injection system comprising: a first syringe for receivingthe first fluid and a first plunger movable within a barrel of the firstsyringe to pressurize the first fluid for delivery to the patient'sblood vessel; and a second syringe for receiving the second fluid and asecond plunger movable within a barrel of the second syringe topressurize the second fluid for delivery to the patient's blood vessel;providing an external restriction member on an outer circumference of atleast one of the first syringe and the second syringe; and adjusting aninner diameter of the external restriction member to adjust a permittedswelling of the at least one of the first syringe and the secondsyringe.
 14. The method of claim 1, wherein adjusting at least one ofthe first flow profile of the first flow rate and a second flow profileof the second flow rate comprises controlling one of the first flow rateand the second flow rate using an equalizing flow valve based on theother of the first flow rate and the second flow rate.
 15. The method ofclaim 1, wherein adjusting at least one of the first flow profile of thefirst flow rate and a second flow profile of the second flow ratecomprises adjusting at least one of the first flow rate and the secondflow rate before delivery of at least one of the first fluid and thesecond fluid based on at least one of known operating fluid pressure andcapacitance of a multi-fluid injection system used to deliver the firstfluid and the second fluid.
 16. The method of claim 1, wherein adjustingat least one of the first flow profile of the first flow rate and asecond flow profile of the second flow rate comprises increasing atransition time between delivering one of the first fluid and the secondfluid and delivering the other of first fluid and the second fluid. 17.A multi-fluid injection system configured to maintain an overall flowrate during a sequential delivery of at least two fluids to a patient'sblood vessel, the system comprising: a processor configured to controlthe multi-fluid injection system to: deliver at least a first fluid intothe patient's blood vessel at a first flow rate; deliver at least asecond fluid into the patient's blood vessel at a second flow rate; andadjust at least one of a first flow profile of the first flow rate and asecond flow profile of the second flow rate to dampen a transientincrease in the overall flow rate during a transition between deliveringone of the first fluid and the second fluid to delivering the other ofthe first fluid and the second fluid.
 18. The controller of claim 17,wherein the processor is further configured to control the multi-fluidinjection system to increase a transition time between delivering one ofthe first fluid and the second fluid and delivering the other of thefirst fluid and the second fluid.
 19. The controller as claimed in claim17, wherein the processor is further configured to control themulti-fluid injection system to delay the delivery of one of the firstfluid and the second fluid until the other of the first fluid and thesecond fluid reaches a predetermined flow rate.
 20. The controller asclaimed in claim 17, wherein the processor is further configured tocontrol the multi-fluid injection system to over-deliver a predeterminedvolume of at least one of the first fluid and the second fluid duringdelivery of the at least one of the first fluid and the second fluid.